The Source of the Early-Negative Blood Oxygenation Signal

Hiro Fukuda¹, Alberto Vazquez¹, Seong-Gi Kim¹

Relationships between changes in oxygen saturation level in emerging veins and the presence of early dip in blood oxygenation signal was examined. When oxygen consumption increases in active parenchyma, it causes oxygen saturation levels to decrease and increases deoxyhemoglobin in blood. These changes are expected to be observed in emerging pial veins because of blood draining. We found that an increase in CBV contributes dominantly to the early dip when CBF response is fast while a decrease in blood oxygen saturation level due to an increase in tissue oxygen consumption also contributes to the dip when CBF response is slow.